A&P2 Week1 Review of A&P1

Neuron

Cell that sends and receives sign

Neuroglia

support, protect, and nourish neurons.

Effectors

muscles, glands, and other neurons that respond to signals

What are the three functional steps of the nervous system?

Sensory input → Integration → Motor output.

Sensory input

Information collected by receptors and sent to the CNS

Integration

Processing and interpretation of information in the CNS

Motor output

Response sent from CNS to effectors

Functions of neurons

Send/receive signals, generate graded and action potentials, release neurotransmitters.

Functions of neuroglia

Unipolar neuron

One process extending from the cell body.

Bipolar neuron

One dendrite and one axon.

Multipolar neuron

Dendrite

Cell body (soma)

Contains nucleus and integrates signals.

Axon hillock

Axon

Conducts action potentials away from the cell body.

Axon terminal

Releases neurotransmitters.

Synapse

Presynaptic cell

Cell sending the signal.

Postsynaptic cell

Cell receiving the signal.

Synaptic cleft

Gap between presynaptic and postsynaptic cells.

Neurotransmitter

Chemical messenger released at a synapse.

Myelin sheath

Insulating covering around axons that increases conduction speed.

Schwann cells

Produce myelin in the PNS; one Schwann cell myelinates one axon segment.

Oligodendrocytes

Produce myelin in the CNS; one cell can myelinate multiple axons.

Astrocytes

Node of Ranvier

Gap between myelin segments where action potentials regenerate.

How does myelin affect conduction?

Allows action potentials to jump node to node (saltatory conduction), increasing speed.

Resting membrane potential

Membrane voltage of about −70 mV when the neuron is not signaling.

Why is the inside of the cell negative at rest?

Negative proteins remain inside and more K+ leaves than Na+ enters.

Sodium-potassium pump

Uses ATP to move 3 Na+ out and 2 K+ in.

Purpose of the sodium-potassium pump

Maintains resting membrane potential.

Graded potential

A local change in membrane potential from rest.

Where do graded potentials occur?

Local depolarization

Example of local depolarization

−70 mV to −65 mV.

Local hyperpolarization

Membrane becomes more negative (away from threshold).

Example of local hyperpolarization

What causes depolarization?

Opening sodium channels and Na+ entering the cell.

What causes hyperpolarization?

Opening potassium channels and K+ leaving the cell.

Threshold

Membrane potential required to trigger an action potential.

Threshold value

Approximately −55 mV.

Action potential

Rapid electrical signal that travels down the axon.

Where does an action potential begin?

Axon hillock.

Depolarization phase

Voltage-gated Na+ channels open and Na+ enters the cell.

Repolarization phase

Voltage-gated Na+ channels close and K+ channels open.

Hyperpolarization phase

K+ continues leaving the cell, making the membrane more negative than resting.

Refractory period

Time during which another action potential is difficult or impossible to generate.

What determines action potential speed?

Sequence of signal flow through a neuron

Dendrite → Soma → Axon hillock → Axon → Axon terminal.

What happens when an action potential reaches the axon terminal?

Voltage-gated calcium channels open.

Role of calcium in synaptic transmission

Triggers neurotransmitter release by exocytosis.

Steps of synaptic transmission

Action potential arrives → Ca2+ enters → neurotransmitter released → neurotransmitter binds receptor → ion channels open → postsynaptic response occurs.

Postsynaptic receptors

Proteins that bind neurotransmitters and cause a cellular response.

Chemically gated sodium channels

Open when neurotransmitters bind, causing depolarization.

Neuromuscular junction (NMJ)

Specialized synapse between a motor neuron and skeletal muscle.

Neurotransmitter at the NMJ

Acetylcholine (ACh).

What happens when ACh binds its receptor?

What happens after neurotransmitters are released?

They are broken down, diffuse away, or are taken back up by the presynaptic cell.

Enzyme that breaks down ACh

Acetylcholinesterase (AChE).

Reuptake

Effectors of the nervous system

Muscles, glands, and neurons.

Fastest type of signal conduction

Myelinated axons using saltatory conduction.

Major ions involved in nerve signaling

Na+, K+, and Ca2+.

Resting membrane potential value

Threshold value

−55 mV.

Hyperpolarization example

−75 mV.

Depolarization example

−65 mV.